put those that wore them to much incon venience. 1. In the winding them up; because the mechanism which put the alarm in motion performed its action every twelve hours, consequently the alarm could not be set longer than twelve hours before-hand. As many people are in the habit of winding up their watches in the morning, and may not have occasion for the alarm till the next day, they were of course under the necessity of winding up again the alarm motion at night. 2. In setting them to time; because on the most ancient alarmwatches there was a double dial-plate, which went round, and always moved with the hour-hand; it was marked with the twelve figures, and the hour-hand had a small tail, to which the user turned that hour on the smaller dial-plate at which he wished the alarm to perform. On the more modern ones they have set aside the dial-plate, and placed a hand that does not go round with the hourhand, but is moved to the hour at which it is wished the alarm should act, where it remains fixed until the hour-hand reaches it, when the alarm goes off. From this it is evident that they could neither be wound up nor brought to act at pleasure." Having enumerated various other defects and imperfections, he adds, "the newly-invented warning watch does away all these defects; both the movement and the warning motion can be wound up together, and the latter as long before-hand as you please. To set it to the hour you wish, there is no need of opening the case, nor of touching the hand, which obviates the necessity

of making the warning-hand so stout as in the old alarm-watches: indeed, it may be made very taper and light. The interior construction of the watch also is extremely simple, there being but one additional wheel with its barrel to an or dinary movement; consequently, the wheels altogether are not crowded for want of space. The detent is the prin cipal object, as has been seen in the old alarm-watches; that now introduced is an entire new invention, and affects the movement of the watch in no way whatever: so long as the warning-hand is not set, there is no communication between that part and the movement. The warning-hand is fixed on in the same manner as the hands of the hour and minutes, and the motion-wheels are placed similar to those of an ordinary watch. In the modern alarm-watches fault has been found with the bell not making a noise sufficiently strong; those adapted to the present invention are so effective that they can be heard in one floor while hung up in another. The principle of this inven tion deprives the wearer of fear of deranging it, and even allows him no op portunity for mismanagement; in short, it offers every desirable convenience at a little expence. The warning-watch will act at pleasure during the whole day, without opening the case or winding it up a new.

"The simplicity of the mechanism is a matter of peculiar consideration to the manufacturer, since it requires but little expence, and can be applied to watches of any price."

M'

ROYAL SOCIETY OF LONDON. [R. DAVY, in the Bakerian lecture of last year, laid before this learned body, the result of various new researches on the subject of his electrochemical discoveries; discoveries, which, if hereafter proved to be founded in truth, will render his name illustrious among every future generation of his Countrymen. The paper to which we have referred, and an account of which will be given in this and the following Numbers, contains (1.) An account of some new experiments on the metals

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from the fixed alkalies: (2.) Experiments on nitrogen, ammonia, and the amal gam from ammonia: (S.) On the metals of the earths; and (4.) Considerations of theory, illustrated by new facts. shall take up these subjects in the ur der in which they stand, that the present and succeeding volumes of the Monthly Magazine may continue to give, as the former volumes have given, a connected series of the facts and principles discovered and illustrated by this very able philosopher and chemist.

With regard to the experiments on the metals

metals from the fixed alkalies, he states, that the generality of enlightened chemists who have repeated the experiments on potash and soda, have expressed themselves perfectly satisfied both with the facts and the conclusions drawn from them. As exceptions, he notices the opinions of Gay Lussac, Thenard, and Ritter, who are willing to suppose that potassium and sodium are compounds of potash and soda, with a portion of hydrogen. The argument on which MM. Gay Lussac and Thenard depend is this: they say, that they heated potassium in ammonia, and that they found that a considerable quantity of ammonia was absorbed, and hydrogen produced, and that the potassium became converted into an olive-coloured fusible substance; by heating this substance strongly, they obtained threefifths of the ammonia again, two-fifths as ammonia, one-fifth as hydrogen and nitrogen; by adding a little water to the residuum, they procured the remaining two-fifths, and found in the vessel in which the operation was carried on, nothing but potash. Again, it is stated, that by treating a new quantity of metal with the ammonia disengaged from the fusible substance, they again obtained hydrogen and an absorption of the ammonia; and, by carrying on the operation, they affirin, that they can procure from a given quantity of ammonia more than its volume of hydrogen.

Whence, they ask, can the hydrogen proceed? Shall it be admitted that it is from the aminonia? but this, say they, is impossible; for all the ammonia is reproduced. It must then come from the water which may be supposed to be in the ammonia, or from the inetal itself. But the experiments of M. Berthollet, jun. prove that ammonia does not contain any sensible quantity of water. Therefore, say they, the hydrogen gas must be produced from the metal; and as, when this gas is separated, the inetal is transformed into potash, the metal appears to be nothing more than a combination of hydrogen, and that alkali.”

Mr. Davy controverts this statement, affirming that the results of numerous experiments conducted in the presence of members of the Royal Society, are, when the processes are conducted with accuracy, totally different from what the French chemists assume. "In propor tion," says he, "as more precautions are taken to prevent moisture from being communicated to it, so, in proportion, is

less ammonia generated; and I have seldom obtained as much as of the quantity absorbed. And I have never procured hydrogen and nitrogen, in the proportions in which they exist in ammonia; but there has been always an excess of nitrogen."

He now gives an account of other processes conducted with the most scrupuious attention; and observes, that in all experiments of this kind, a considerable quantity of black matter, separated du ring the time the potassium in the tube was made, to act upon water.

This substance was examined. It was in the state of a fine powder. It had the lustre of plumbago; it was a conductor of electricity. When it was heated, it took fire at a temperature below ignition; and after combustion, nothing remained but minutely divided platina.

I exposed some of it, says he, to heat in a retort, containing oxygen gas; there was a diminution of the gas; and a small quantity of moisture condensed on the upper part of the retort, which proved to be mere water.

I made two or three experiments, with a view to ascertain the quantity of this substance formed, and to determine more fully its nature. I found that in the process in which from 3 to 4 grains of potassium were made to act upon ammonia in a vessel of platina, and afterwards distilled in contact with platina, there were always from 4 to 6 grains of this powder formed; but I have advanced no further in determining its nature, than in ascertaining that it is platina combined with a minute quantity of matter, which affords water by combustion in oxygen.

In the processes on the action of potassium and ammonia, there is always a loss of nitrogen, a conversion of a portion of potassium into potash, and a production of hydrogen. When copper

tubes are employed, the hydrogen bears a smaller proportion to the nitrogen, and more potassium is revived.

In these experiments, in which platina has been used, there is little or no loss of potassium or nitrogen; but a loss, smaller or greater, of hydrogen.

He then describes an experiment on the action of sodium on ammonia with the same precautions. He took 3 grains of sodium, and found that it absorbed 91 of ammonia, and produced 4-5 of hydrogen, and the fusible substance, which was very similar to that of potassium distilled, did not give of

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As sodium does not act so violently upon oxygen as potassium, and soda does not absorb water from the atmosphere with nearly so much rapidity as potash, sodium can be introduced into ammonia, much freer from moisture than potassium. Hence, when it is heated in ammonia, there is no effervescence, or at least one scarcely perceptible. Its tint changes to bright azure, and from bright azure to olive green; it becomes quietly and silently converted into the fusible substance, which forms upon the surface, and then flows off into the tray. It emits no elastic fluid, and gains its new form evidently by combining with one part of the elementary matter of ammonia, whilst another part is suffered to escape in the form of hydrogen.

In speaking of M. Curadeau's theory, that the metals of the alkalies are composed of the alkalies merely united with charcoal, he says, that the investigation upon which this gentleman has founded his conclusions is easily accounted for, since it was evident he had been misled by the existence of charcoal, as an accidental constituent in the metals that he employed. M. Ritter's argument in favour of potassium and sodium being compounds of hydrogen, is their extreme lightness, an argument easily answered: sodium absorbs much more oxygen than potassium, and, on the hypothesis of hydrogenation, must contain much more hydrogen; yet though the soda is said to be lighter than potash in the proportion of 13 to 17, sodium is heavier than potassium in the proportion of 9 to 7. According to Mr. Davy's own theory, this circumstance might be expected: for potassium has & much stronger affinity for oxygen than sodium, and must condense it much more, and the resulting higher specific gravity of the combination, is a necessary consequence. M. Ritter has stated, that of all the metallic sub

stances he tried for producing potassium by negative voltaic electricity, tellurium was the only one by which he could not procure it. And he states the very curious fact, that when a circuit of elec tricity is completed in water, by means of two surfaces of tellurium, oxygen is given off at the positive surface, no hydrogen at the negative surface, but a brown powder, which he regards as a hydruret of tellurium, is formed and sepa rates from it; and he conceives that the reason why tellurium prevents the metallization of potash is, that it has a stronger attraction for hydrogen than that alkali.

These circumstances of the action of tellurium upon water, are so different from those presented by the action of other metals, that they can hardly fail to arrest the attention of chemical enqui rers. Mr. Davy made some experiments on the subject, and on the action of tellurium on potassium, and finds that, in. stead of proving that potassium is a com. pound of potash and hydrogen, they confirm the idea of its being as yet like other metals undecompounded.

When tellurium is made the positive surface in water, oxygen is given off, when it is made the negative surface, the voltaic power being from a battery composed of a number of plates exceed. ing 300, a purple fluid is seen to separate from it, and diffuse itself through the water; the water gradually becomes opaque and turbid, and at last deposits a brown powder. The purple fluid is a solution of a compound of tellurium and hydrogen in water; which, in being diffused, is acted upon by the oxygen of the common air, dissolved in the water, and gradually loses a part of its hydrogen, and becomes a solid bydruret of tellurium. The compound of hydrogen and tellurium produced at the negative pole, when uncombined, is gaseous at common temperatures; and when muriatic acid, or sulph ric acid, are present in the water, it is not dissolved, but is given off, and inay be collected and examined. From a variety of other' facts stated with much clearness, and carrying with them incontestable evidence, the professor adds: "After these illus trations, Ftrust the former opinions which I ventured to bring forward, concerning the metals of the fixed alkalies, will be considered as accurate, and that potassium and sodium can with no more propriety be considered as compounds, than any of the common metallic substances;

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and